1. Field of the Invention
The present invention relates to a motor drive device.
2. Description of the Related Art
Conventionally, there is known a motor drive device having a constant voltage power supply. In order to drive a brushless DC motor using an AC voltage source, the constant voltage power supply converts an AC voltage supplied from the AC voltage source into a DC voltage. Further, conventionally, there is known a constant voltage power supply having a smoothing capacitor and a rectifier circuit for rectifying an AC voltage.
A conventional constant voltage power supply is disclosed in, e.g., Japanese Patent Application Publication No. 1995-123721. As disclosed in Japanese Patent Application Publication No. 1995-123721, in a constant voltage power supply formed by simply combining a smoothing capacitor with a rectification bridge circuit for rectifying an AC voltage, there occurs a problem that a power factor is reduced (see Paragraphs [0002] and [0005] and FIGS. 4 and 5). Therefore, in the constant voltage power supply disclosed in Japanese Patent Application Publication No. 1995-123721, the power factor is improved by using a transformer (see Paragraph [0020]).
However, in the case where the constant voltage power supply has a transformer, the constant voltage power supply is increased in size. Further, the transformer causes a power loss such as heat generation to thereby reduce the efficiency. Therefore, the transformer is not suitable for the constant voltage power supply used in the motor drive device.
In view of the above, at least an embodiment of the present invention provides a motor drive device having a constant voltage power supply capable of suppressing a decrease in efficiency while improving a power factor.